When you say "big growth", are you actually focused on the ratio between digital and physical or are you talking about the number that Nintendo presents as digital sales ratio? Because the latter has been largely driven by NSO subscriptions growing in number.
There hasn't been a big uptick in digital being chosen over physical in recent years, outside of the unique combination of Animal Crossing (a game that gets played for a short time every day has much higher acceptance as digital copy than the average game) and the COVID-19 measures that limited the purchasing options of people. You also have to consider that Nintendo has given various benefits to digital over physical, such as 5-10 times as many gold points or vouchers for first party games, but physical remains the prefered option by a large margin and the digital share has been growing at a modest pace at best. The growth of digital won't be continuous until it eventually hits 100%, because it will absolutely hit a brick wall long before that.
The benefits of physical will remain too strong for digital to be seen as an equal alternative. Physical provides actual game ownership including the ability to lend and borrow without hassle as well as the option to sell. Physical also exists in an open marketplace where a lot of retailers compete for attention and therefore offer better discounts than what you'll find on the Nintendo-owned eShop. Physical is also the only viable option for game collectors which have a much stronger presence on Nintendo consoles than on other consoles.
Believing in digital becoming so big on a Nintendo console that it will prevent 10m+ physical copies being sold means to believe that Nintendo's digital policies will become so good that the vast majority of the market will be okay with buying digital over physical.
The former since the Switch does have a higher ratio for that than the 3DS did. Nintendo is basically a generation behind on that ratio so in a few years or so should get to about where Sony is at now. Physical does have benefits but I think the convenience of digital will win over the vast majority over time. I don't want the benefits of physical to ever go away but convenience is a very powerful force for the masses.
I do believe the vast majority of the market will become ok with that though admittedly Nintendo's policies could slow down that process for Nintendo systems. Their refund policy will hopefully not take too long to get improved.